A resveratrol-based P/Si-containing hyperbranched flame retardant for simultaneously enhancing fire safety and mechanical properties of epoxy thermosets

Epoxy resin is renowned for its admirable comprehensive properties, but its inherent brittleness and poor fire safety severely limit its practical application in high-tech fields. Therefore, improving the fire safety and toughness of epoxy thermosets while maintaining their strength and thermal stability is both urgent and challenging. In this study, a novel hyperbranched polymer (HBPDR-DPP) has been synthesized via a one-pot, two-step process using dichlorodiphenylsilane, resveratrol, and diphenylphosphinic chloride. This polymer was then incorporated into high-performance epoxy thermosets. The resulting thermoset, containing 4 wt% HBPDR-DPP, exhibited an impressive limiting oxygen index (LOI) of 30.2 %, along with a 26.0 % decrease in peak heat release rate (PHRR) and a 10.9 % reduction in total smoke production (TSP) compared to the unmodified epoxy thermoset. These notable improvements can be primarily attributed to the synergistic carbonization effects of the silicon- and phosphorus-containing segments in HBPDR-DPP. Meanwhile, the 4 wt% HBPDR-DPP-modified epoxy thermoset exhibited significant improvements in mechanical properties, with tensile strength, flexural strength, and impact strength increasing by 37.8 %, 54.6 %, and 83.4 %, respectively. These enhancements can be attributed to the hyperbranched structure and the combination of rigid aromatic units with flexible Si-O chains in HBPDR-DPP. Moreover, the EP/HBPDR-DPP thermoset demonstrated excellent thermal stability. This study presents a simple and effective strategy for enhancing both the fire safety and mechanical properties of epoxy thermosets, offering valuable insights for the development of high-performance thermosetting materials.